The present invention relates to the field of form, fill and seal packaging systems, and more particularly, to an improved product stripper and bag sealing operation that may be adjusted for handling different size bags for maximum packaging speed.
Machines and related methods for forming, filling and sealing of packages made from a continuous film are well known in the art. These machines typically comprise a supply of packaging film, a former for converting the film into a continuous hollow tube and reciprocating jaws on a movable carriage for stripping, sealing and cutting the tube into a consecutive series of filled packages, namely pillow-shaped bags.
The sealing jaws in a typical packaging machine of this type are brought together in two steps. The first step closes the jaws just sufficiently to bring the stripper plates into engagement to flatten the package film tube. The stripper plates are moved relative to the film tube in order to strip any product from the zone of the tube to be subsequently sealed. The second step completes the closing of the bag by bringing the sealing jaws together to form the seal and to cut the bag from the tube.
After each bag is formed, the jaws are typically moved outwardly from the film tube by a fixed distance and moved relative to the tube back to the home position in readiness for producing the next bag from the continuous film tube.
In one known form of the machine and method according to form, fill and seal packaging principles, the sealing jaws are mounted on a carriage that is reciprocated in a longitudinal direction with respect to the film tube to both strip and feed the film. The carriage slides along vertical support rods and the machine control moves the sealing jaws in and out with respect to the tube in order to form the package. During the last portion of the movement of the carriage, the sealing jaws are in the sealing position clamping the film tube and the motion is operative to feed the next bag length. The bag length is actually determined by a photocell sensor reading registration marks on the film with the sealing jaws opening to release the film before reaching the full travel. In this manner, the length of the bag is controllable within a relatively narrow range.
This type of stripper and sealing apparatus has proven highly successful in practice and a large number of machines of this type are in operation today. One of the most successful machines of this type is shown and claimed in the prior U.S. patent entitled Sealing Carriage, U.S. Pat. No. 3,616,087, issued Oct. 26, 1981 and assigned to the same assignee as the present invention. Even with the substantial success of this type of prior machine and method, demands have been made on the industry for substantially increased speed and efficiency. In response to this demand, I have invented a new system for feeding the packaging film, which system is disclosed and claimed in my prior U.S. patent application entitled Packaging Film Feeding Apparatus and Method, Ser. No. 941,694, filed Dec. 15, 1986, and assigned to the same assignee as the present invention, now U.S. Pat. No. 4,727,707, issued Mar. 1, 1988. This new film feeding concept employs endless belts that engage the sides of the film that are driven by stepping motors and controlled by computer. The feeding of the film is maximized in terms of speed and efficiency by constantly accelerating the film over the first half of the driving time and constantly decelerating the film over the remaining half. This feature, along with others provides substantial increases in the efficiency and speed of the packaging operation and is expected to obtain wide acceptance among the industry.
In order to obtain the maximum film feeding efficiency and speed in accordance with my prior invention set forth in the previously filed application, it has been found necessary to also increase the efficiency and speed of the stripping and sealing operation. In the prior devices, such as shown in the prior U.S. Pat. No. 3,616,087, the sealing jaws are moved substantially the same distance during each packaging cycle, both along the longitudinal axis of the film as well as toward and away from the film in order to seal each individual bag. As a result, even with improved film feeding as set forth in my previous invention, the complete packaging machine cannot operate at full efficiency because the slower, old style sealing jaw movement is a limiting factor.
In addition to the need for increased efficiency and speed in order to match my new film feeding concept, there is a need to provide a stripper and sealing jaw apparatus that can be adjusted or programmed to operate on a broad range of bag sizes. A breakthrough in technology of this nature allows providing a standard carriage for the sealing jaws for minimum cost to the manufacturer while assuring that the stripper/sealing jaw operation can match the increased film feeding speed for any size bag.